Semiconductor chips or dies typically are manufactured from a semiconductor material such as silicon, germanium, or gallium/arsenide. An integrated circuit or other active feature(s) is incorporated in the device adjacent one surface (often referred to as the “active surface”) of the device. The active surface typically also includes input and output contacts to facilitate electrical connection with another microelectronic component.
Flip-chip technology, including ball grid array packaging technology, is widely used in the microelectronics industry. In flip-chip technologies, a microelectronic component (e.g., a semiconductor die) having a pattern of conductive pads on an active surface is joined to a second microelectronic component, typically a higher level substrate such as a printed circuit board. Electrical contacts on the second microelectronic component are arranged in a mirror image to the contacts on the semiconductor die. Conductive structures—typically solder bumps (as exemplified by the so-called C-4 technology), conductive epoxy bumps or pillars, conductor-filled epoxy, or an anisotropically “Z-axis” conductive elastomer—are used to join the contacts on the first microelectronic component with corresponding contacts on the second microelectronic component, establishing electrical communication between the two microelectronic components.
Microelectronic components such as semiconductor dies often are sensitive to mechanical damage, external contamination, and moisture. To ameliorate these environmental factors, many microelectronic component assemblies are packaged in a polymeric or ceramic material that helps protect the underlying component(s). If these components are to be attached to a second microelectronic component using flip-chip techniques, the contacts of the first microelectronic component assembly must be electrically accessible through the package.
Providing a reliable electrical connection through the package can be problematic. In one approach, a solder ball or other conductive element is provided on the contacts of a semiconductor die or other microelectronic component. The solder-bumped component is then encapsulated in plastic. If conventional transfer molding techniques are employed in forming the plastic package, the resin may substantially cover the solder balls or other connectors. To provide suitable electrical connections, this structure must be ground down using chemical-mechanical polishing (CMP) techniques, exposing a flat surface of the previously covered solder. To attach this microelectronic component to a second microelectronic component, another conductive structure, e.g., another solder ball or solder bump, must be applied to the exposed solder surfaces. This requires handling the microelectronic component assembly a number of times when transferring the assembly from one manufacturing stage to another. The CMP process can also be relatively messy, detrimentally affecting the microelectronic component assembly.
In other packaging techniques, the encapsulant is formed before the solder or other conductive structure is deposited. In one technique, the microelectronic component is completely encapsulated in the encapsulant material and openings subsequently are formed in the encapsulant to expose the contacts or other conductive structures of the microelectronic component. Again, though, this requires multiple handling steps and precise control of the process for forming the holes in the package without damaging the conductive structures intended to be accessed through the holes.
In other approaches, the mold element used in molding the encapsulant about the microelectronic component includes projections that abut the electrical contacts of the microelectronic component. When the encapsulant is injected into the mold, the encapsulant should flow around the projections, leaving an indentation through which the underlying contact is accessible. (One example of such a process is outlined in U.S. Pat. No. 6,028,356, the entirety of which is incorporated herein by reference.) In such processes, however, the encapsulant material tends to squeeze between some of the projections and the electrical contacts. This will leave a thin flash coating of the encapsulant on the electrical contacts. Accordingly, the packaged microelectronic component assembly typically must be further processed, e.g., in an etching operation, to remove this flash coating; failure to do so will jeopardize reliable electrical connections between the packaged component and other microelectronic components.